Seedling inoculation distinguishes lodgepole pine families most and least susceptible to gall rust

Resistance of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) to western gall rust (Endocronartium harknessii (J.P. Moore) Y. Hiratsuka) was compared between 21-year field infection trials and inoculation of 2-month-old seedlings. The seedlings were produced from seed stored since the original field plantings. Virtually all of the seedlings from families identified as susceptible in the field produced galls in the inoculation trial, only 1% of seedlings from these families did not develop galls. Nearly half the seedlings in families classed as resistant in the field trials did not form galls 13 months after inoculation. Only one of these seedlings developed galls in the following 2 years. Seedling inoculation provides a simple early test to assess field resistance to gall rust of lodgepole pine seedlots, and an efficient way to cull at least the most susceptible ones.